Apical k+ conductance in maturing rabbit principal cell.
Satlin, Lisa M., and Lawrence G. Palmer.
Department of Pediatrics, Albert Einstein College of Medicine, 1410
Pelham Pkwy South, Bronx, New York 10461 and Department of Physiology
and Biophysics, Cornell University Medical College, New York, New
York 10021
APStracts 3:0228F, 1996.
Net K+ secretion is not detected in CCDs isolated from newborn rabbits
and perfused in vitro. To establish whether a low apical K+
permeability of the neonatal principal cell limits K+ secretion early
in life, we used the patch-clamp technique in split-open CCDs
isolated from maturing rabbits to study the properties and density of
conducting K+ channels in principal cells. With KCl in the pipette
and a NaCl solution warmed to 37oC in the bath, inward currents with
a conductance of 42 pS were observed in 0% (0 out of 13, or 0/13),
10% (2/21), 18% (5/28), 29% (4/14) and 56% (10/18) of cell-attached
patches obtained in 1-, 2-, 3-, 4-, and 5-wk-old animals,
respectively. The conductance and reversal potential of this channel
led us to suspect that it represented the low conductance K+ channel
previously described in the rat CCD by Palmer et al (J. Gen. Physiol.
104:693,1994). The mean number of open channels per patch (NPo)
increased progressively (p<0.05) after birth, from 0 at 1 wk,
to 0.06+/-0.04 at 2 wk, to 0.40+/-0.18 at 3 wks, to 0.74+/-0.41 at 4
wks, and to 1.06+/-0.28 at 5 wks. The increase in NPo appeared to be
due primarily to a developmental increase in N, which is the number
of channels; Po remained constant at 0.5 for all channels identified
after the 2nd wk of life. The increase in number of conducting K+
channels during postnatal life is likely to contribute to the
maturational increase in net K+ secretion in the CCD.
Received 1 October 1996; accepted in final form 13 December 1996.
APS Manuscript Number F275-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996